Much of the world's petroleum resources are in the form of bitumen (heavy and light oil fractions) mixed with sands and clays. These deposits are generally referred to as oil sands. Extraction of the bitumen from this source requires a larger input of energy relative to that required for conventional crude oil. Perhaps more significantly, the process also requires the use of fresh water and leaves behind large, but temporary, tailings ponds. The environmental impact of mining operations in, for example, the Canadian oil sands, has been the subject of much media discussion, in particular during the 2009 Copenhagen Summit.
Oil sand bitumen contains significant quantities of asphaltenes, which can form deposits in wells and pipelines, as well as insoluble nanosized aggregates under certain conditions (Murgich J, Abanero J A, Strausz O P. (1999) Energy Fuels. 13, 278-286). Asphaltenes are typically defined operationally as the fraction of oil that is pentane-insoluble and benzene-soluble. In some definitions, asphaltenes are defined operationally as the fraction of oil that is n-heptane insoluble and toluene-soluble. In both cases, asphaltenes are soluble in an aromatic solvent but insoluble in a low molecular weight saturated aliphatic solvent. Upgrading this bitumen requires the treatment/removal of asphaltenes, which seriously reduces the cost-effectiveness associated with the process. This is complicated by the fact that asphaltene structure and composition differ depending upon their source (Mansoori G A. (1988) OPEC Review. 12, 103-113). However, they are thought to be composed of central structures of extended aromatic systems with alkyl or alkylthiol substituents and/or bridges (Groenzin H, Mullins O C. (2000) Energy Fuels. 14, 677-684 and Tan X, Fenniri H, Gray M R. (2008) Energy Fuels. 22, 715-720.).
There remains a need in the art for new uses of asphaltenes. New uses for asphaltenes help reduce the environmental burden of bitumen extraction in which asphaltenes are often considered a waste product.